What Does the Large Intestine Do?

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The large intestine, or colon, receives what's left of a person's meal after most of the nutrients have been extracted from it by the rest of the gastrointestinal tract. This material, called chyme, is made up of salts, water, bodily secretions and indigestible material, such as dietary fiber. The colon absorbs the water and salts from the chyme and slowly moves it along toward the anus.

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The colon is lined with many varieties of bacteria that help it process the chyme. Mucus also lubricates the inside of the colon, making the passage of chyme easier.

Unlike the small intestine, the muscles of the large intestine take a long time to contract and relax. Because of this, it takes between 12 and 24 hours for the remains of a meal to be evacuated from the body. The contractions of the colon are controlled by nerves and hormones.

The colon is divided into four parts. The ascending colon is on the right side of the body. It connects with the transverse colon, which crosses the body to the opposite side. There, it meets the descending colon on the left side of the body. The descending colon is connected to the S-shaped sigmoid colon. In humans, the colon is about 5 feet long.